Nondigestible oils which are liquid at body temperature (i.e. at 98.6.degree. F., 37.degree. C.) have a tendency to collect as a liquid mass in the intestine. If these nondigestible oils are not adsorbed by other fecal matter in the intestine, they can pass through the anal sphincter as an oil. This failure to retain the nondigestible oil with the other fecal matter and its passage through the anal sphincter unchanged is referred to as "passive oil loss" (or alternatively as "anal leakage").
Several agents have been proposed for controlling or preventing passive oil loss of nondigestible oils. These agents include higher molecular weight or higher melting solid nondigestible materials, as well as longer chain saturated fatty acids, for example, stearic acid and palmitic acid, or digestible sources of such fatty acids. See, for example, U.S. Pat. No. 4,005,195 (Jandacek, 1977), which discloses the use of solid fatty acids or digestible sources of solid fatty acids; U.S. Pat. No. 4,797,300 (Jandacek et al, 1989) and European patent application 311,154 (Letton, 1989), which disclose the use of certain solid polyol polyesters; and European patent application 352,907 (Howard et al, 1990), which discloses the use of microfibrillated cellulose.
Some of the agents used to control or prevent passive oil loss provide a high level of solids at mouth temperature (e.g., 92.degree. F., 33.3.degree. C.) such that they taste waxy when ingested. Accordingly, intermediate melting polyol fatty acid polyesters have been developed to provide passive oil loss control, while at the same time reducing waxiness in the mouth. See European patent application 236,288 (Bernhardt, 1987) and European patent application 233,856 (Bernhardt, 1987). These intermediate melting polyol polyesters exhibit a unique rheology at body temperatures due to a matrix involving a minimum level of solids (e.g., about 12% or lower) that bind the remaining liquid portion. As a result, these intermediate melting polyol polyesters are sufficiently viscous and have a sufficiently high liquid/solid stability at body temperatures to control passive oil loss. An example of such intermediate melting polyol polyesters are those obtained by substantially completely esterified sucrose with a 55:45 mixture of fully hydrogenated (hardstock) and partially hydrogenated soybean oil fatty acid methyl esters. See Examples 1 and 2 of the above European patent applications.
Liquid nondigestible oils have also been suggested for use in clear cooking and salad oils. However, some of the agents added to these nondigestible oils to control passive oil loss can cause the resulting composition to be cloudy or opaque at room temperature, i.e. at about 70.degree. F. (21.1.degree. C.) or below, instead of clear. This problem of cloudiness or opaqueness can be particularly severe if the oil is stored at refrigerator temperatures, e.g., at about 40.degree. F. (4.4.degree. C.) or below. At refrigerator temperatures, in some formulations visible solids form that can precipitate out. Consumers usually object to cooking and salad oils having solids in them.
It has been discovered that adding hydrophobic silicas to a nondigestible oil not only prevents passive oil loss, but also provides a clear oil.
Silica materials have been added to oils to increase their viscosity. See, for example, U.S. Pat. No. 4,605,563 to Heine et al (1986). The viscosity of the oils is increased by adding from 1-10% of a high melting glyceride and from 2-10% of a highly dispersed pyrogenic silica having submicron particles.
In CRC Critical Reviews in Food Science and Nutrition, Vilotta et al, "Food Applications and the Toxicological and Nutritional Implications of Amorphous Silicon Dioxide", 23 (4), (289-321) the food uses of silicas are described. In addition to their use as suspending agents or thickening/thixotropic agents in oils, they can be added to foods for anti-caking and dispersion. See for example U.S. Pat. No. 4,375,483 issued to Shuford et al (1983) (salt dispersed in an oil), U.S. Pat. No. 4,834,991 issued to Porcello et al (1989) (filler cream), U.S. Pat. No. 4,652,458 issued to Frost et al (1987) (lipid composition), U.S. Pat. No. 4,103,038 issued to Roberts (1978) (synthetic egg), and U.S. Pat. No. 3,669,681 issued to Shoaf et al (1972) (fat for toaster pastry).
Silica has also been used as an anti-anal leakage (i.e. passive oil loss control) agent in a nonfat low calorie food composition in which part of the fat is substituted by a liquid siloxane polymer. See U.S. Pat. No. 4,925,692 to Ryan (1990) where anti-anal leakage agents such as stearic acid or silica are used to prevent leakage of the liquid siloxane through the anal sphincter.
It is an object of this invention to add-hydrophobic silicas to a liquid nondigestible oil to control or prevent passive oil loss.
It is also an object of this invention to obtain reduced calorie potato chips and other fried, or fat-containing, low moisture foods that have passive oil loss control, yet have less waxiness and substantially unaltered flavor display.
It is yet another object of this invention to provide reduced calorie cooking and salad oils formulated from liquid nondigestible oils that have passive oil loss control, yet are clear at room temperature, and preferably are clear at refrigerator temperatures.
It is a further object to produce a non-digestible oil which can be used to replace from 10% to 100% of the oil in a high or low moisture foods without causing passive oil loss. These and other objects will be evident from the description herein.